This invention relates to a control apparatus for a multifunction device for efficient control of an image input unit such as a scanner and an image output unit such as a printer.
Copiers and facsimile machines which combine an image input unit such as a scanner and an image output unit such as a printer, as well as computer systems equipped with these as separate units, are now in practical use. Such systems require the efficient processing of enormous amounts of data in order to handle image data.
Such systems rely upon DMA transfer using a plurality of bus masters in order to transfer data. In a case where a plurality of bus masters execute processing in successive fashion, a series of processing operations is conceivable in which data in memory is first subjected to processing A (bus master 1) and then to processing B (bus master 2), after which the processed data is sent to a bus master 4.
If a DMA (Direct Memory Access) function in which each bus master reads the data from the memory and then writes the processed data back to the memory is available when performing such processing, usually the pertinent software sets DMA in such a manner that bus master 1 executes processing A. After master 1 has completed all processing, the software interrupts the processor and sets DMA in such a manner that processing will be terminated. After this processing is completed, the software sets DMA in such a manner that bus master 4 reads data out of the memory. Thus, in order to perform this series of processing operations, it is necessary to execute processing by software in such a manner that after the completion of one processing operation is verified, the next processing operation is started.